Composite polymer blast media

ABSTRACT

A method for making a polymeric blast media, and a product of this method. The first step involves blending a melamine compound with a cellulosic material and compression molding said first blend to produce a compression molded first blend. This first blend is then cooled and then ground. In the next step of this method, a urea compound is blended with a nano-clay material to produce a second blend and compression molded. This compression molded second blend is then ground to produce a particulate second blend. The particulate first blend is then blended with the particulate second blend. A blast media product of this method is also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority under U.S. Provisional PatentApplication Serial No. 60/208,624, filed Jun. 1, 2000 and U.S.Provisional Patent Application Serial No. 60/226,135, filed Aug. 18,2000.

BACKGROUND OF THE INVENTION

[0002] 1. Technical Field

[0003] The present invention relates to polymer composite materials andmore particularly to polymer composite materials used as abrasives andmore particularly as a blast media. Still more particularly, thisinvention relates to the use of nano-structure composite materials as anabrasive and a blast media.

[0004] 2. Background Information

[0005] Various methods and compositions are taught in the prior art forthe stripping of organic coatings from an underlying metal or compositesubstrate by means of polymer abrasives. Such polymer abrasives have theadvantage of being harder than the organic substrate but softer than theunderlying substrate.

[0006] U.S. Pat. No. 4,731,125, for example, discloses a process wherebypaint is removed from composites by blasting with urea-formaldehydeplastic particles having a Mohs scale hardness of 2.5-3.5 with a flow ata pressure of 40 lb/in².

[0007] U.S. Pat. No. 4,947,591 discloses a process whereby paint isremoved by impact with particles of an acrylic-containing unsaturatedpolyester where the particles are ground from a cured mass so as to haveat least 40 facets per particle.

[0008] U.S. Pat. No. 5,112,406 discloses a process for removing coatingsfrom sensitive hard surface metal composite surfaces, masonry, stucco,plaster or wood by blasting the surfaces with a high velocity fluidstream containing water soluble crystalline sodium sulfate particlesadmixed with a hydrophobic silica or hydrophobic polysiloxaneflow/anti-caking agent.

[0009] U.S. Pat. No. 5,160,547 discloses a process where the surfacesare blasted with water saturated compressed air stream under pressuresof 10-150 psi using sodium bicarbonate particles having particle sizedof 250-300 microns in admixture with a hydrophobic silicaflow/anti-caking agent.

[0010] U.S. Patent No. 5,147,466 discloses fine particles or oil filmswhich are cleaned from the surface by bombarding it with fine frozenparticles of water or other liquids such as glycerin carried in a streamof nitrogen cooled air under relatively low pressure.

[0011] U.S. Pat. No. 5,221,296 discloses abrasives based on finelydivided abrasive particles bonded to one another and/or to a support bymeans of a binder, where the binder is the solid component of an aqueouspolymer dispersion which is obtainable by polymerizing unsaturatedmonomers which can be polymerized by means of free radicals in theaqueous phase of a monosaccharide, oligosaccharide, polysaccharide,oxidatively, hydrolytically and/or enzymatically degradedpolysaccharide, chemically modified monosaccharide, oligosaccharide orpolysaccharide or a mixture of the above.

[0012] U.S. Pat. No. 5,308,404 discloses a process by which contaminantsare removed from substrates by blast cleaning with a media containingabrasive particles obtained by compacting fine particles of the abrasiveinto larger particles having a hardness of 2-5 Mohs and wherein theabrasive can be water (soluble or insoluble) and is preferably sodiumbicarbonate or calcium carbonate.

[0013] U.S. Pat. No. 5,316,587 discloses blast cleaning a sold surfacewhich includes the steps of propelling an abrasive blast medium againsta solid surface suing a water-containing pressurized fluid stream tostrip contaminants form the surface wherein the blast medium compriseswater soluble abrasive particles and a surfactant.

[0014] U.S. Patent No. 5,322,532 discloses a process for removingcontaminants from a substrate comprising blast cleaning the substratewith composite abrasive particles formed by agglomerating particles ofsodium bicarbonate with a aqueous binder solution of sodium carbonate.

[0015] U.S. Patent No. 5,360,903 and U.S. Patent No. 5,367,068 disclosea process whereby a surface is treated with particles of a glassypolysaccharide wherein the apparent hardness of the granules is betweenthat of the coating and of the substrate and the granules are of starch,preferably wheat starch with dextrose equivalent less than 10,preferably unhydrolyzed.

[0016] U.S. Patent No. 5,380,347 discloses a blast media for strippingcontaminants from a solid surface comprising abrasive particles and asurfactant in the form of a granular surfactant-clathrate compoundformed of a surfactant and a water soluble compound having clathrationcapability such as urea. The surfactant reduces the amount ofwater-soluble residues, which remain on the targeted surface andenhances the removal of dirt, grease and oil from the targeted surface.

[0017] U.S. Patent No. 5,427,710 discloses a composition useful forremoving polymeric coatings from flexible and inflexible surfaces whichconsists essentially of a conjugated terpene, an alcohol, anon-conjugated terpene, a surfactant and an organo-clay rheologicaladditive.

[0018] U.S. Patent No. 5,780,619 discloses a starch graftpoly(meth)acrylate blast media which is effective in paint removal. Themedia is superior to a physical blend of the components (i.e., starchand acrylic polymers) and to wither a starch polymer or an acrylicpolymer used singly. The hardness of the media is between 65-90 Shore D.

[0019] A need, however, exists for ways to improve the speed andeffectiveness of such stripping procedures. A need also exists for waysof decreasing the breakdown rate of abrasives used for this purpose.

SUMMARY OF THE INVENTION

[0020] It is an object of the present invention to provide a polymericblast media which efficiently and cost effectively removes organiccoatings from substrates.

[0021] It is a further object of the present invention to provide apolymeric blast media which allows rapid removal of organic coatingsfrom substrates.

[0022] It is a further object of the present invention to provide apolymeric blast media which can be used to remove standard organiccoatings without substantial risk of damage to sensitive metal orcomposite substrates.

[0023] It is a further object of the present invention to provide apolymeric blast media which has a high degree of durability.

[0024] It is a still further object of the present invention to providea polymeric blast media which has favorable surface roughness, almenarc, and water absorbence characteristics.

[0025] These and other objects are met by the present invention which isa method for making a polymeric blast media, and a product of thismethod. The first step involves blending a melamine compound with acellulosic material and compression molding said first blend to producea compression molded first blend. This first blend is then cooled andthen ground. In the next step of this method, a urea compound is blendedwith a nano-clay material to produce a second blend and compressionmolded. This compression molded second blend is then ground to produce aparticulate second blend. The particulate first blend is then blendedwith the particulate second blend.

[0026] In another preferred embodiment, a cross linked cast acrylic isground to a particulate material and blended with the first and secondblends.

[0027] In another preferred embodiment, the particles in the blast mediaare coated with a polyurethane coating.

[0028] In another preferred embodiment, a glass oxide or metal oxidedense particulate material is incorporated with the blast media.

[0029] The present invention also encompasses an abrasive media for theremoval of coating or for the preparation of surfaces prior to coatingor cleaning comprising a thermosetting polymer with an additive, whereinthe additive has a major dimension and a minor dimension and said minordimension is from about 1nm to about 20 nm. The additive may be thenano-clay material, or alternatively may be a polyhedral oligomericsilsesquioxane material.

[0030] The present invention also encompasses a method of making asanding pad for removing an organic coating from a substrate comprisingthe steps of blending a liquid polymeric material with a nano-claymaterial to produce a first blend, blending a cellulosic material withsaid first blend to produce a second blend. This second blend is thenextruded to form a continuous sheet of abrasive material into aplurality of individual pads.

[0031] The blast media of this invention may be used for removal ofstandard aerospace coatings such as epoxy primers and polyurethanetopcoats from very sensitive metal or composite substrates with betterefficiency than was previously available. This media coating can beremoved at accelerated speeds as compared to prior art blast media. Thesafety factor of this media on thin skin aluminum or composite surfacesis high. Coatings can be removed with virtually no damage to suchsubstrates, leaving protective coatings such as cladding and anodizingintact. Also, the durability of this media helps to maintain economicfeasibility in large-scale aerospace applications. Various differentembodiments of this media address specific applications related to theaerospace industry and industry in general. All of these embodimentsmake use of nanometer-sized montmorillonite clay particles, whichimprove surface integrity and provide advantages in the mechanical andthermal properties of the polymer. These results are achieved with noincrease in specific gravity due to the very low amounts ofnano-particle needed, i.e. between {fraction (1/2)}% and 5% by weight.These results demonstrate that the overall increase in efficiency ofthis media is three to four times faster than unfilled polymer while thedurability has more than doubled.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The preferred embodiment of the invention, illustrative of thebest mode in which applicant contemplated applying the principles, isset forth in the following description and is shown in the drawings andis particularly and distinctly pointed out and set forth in the appendedclaims.

[0033]FIG. 1 is a flow diagram illustrating the manufacture of a blastmedia composition representing a preferred embodiment of the presentinvention;

[0034]FIG. 2 is a flow diagram illustrating the manufacture of a blastmedia composition representing an alternate preferred embodiment of thepresent invention with a ground cross linked cast acrylic component;

[0035]FIG. 3 is a flow diagram flow diagram illustrating the manufactureof a blast media composition representing an alternate preferredembodiment of the present invention with another ground cross linkedcast acrylic component;

[0036]FIG. 4 is a flow diagram illustrating the manufacture and use of acomposition representing an alternate preferred embodiment of thepresent invention in which a polyurethane coating is applied to theparticles;

[0037]FIG. 5 is a flow diagram illustrating the manufacture and use of acomposition representing still another alternate preferred embodiment ofthe present invention in which the acrylic component is added in adifferent way;

[0038]FIG. 6 is a flow diagram illustrating the manufacture and use of acomposition representing an alternate preferred embodiment of thepresent invention in which a Type III melamine composition and a Type VIallyldiglycol carbonate composition is included in the composite side;

[0039]FIG. 7 is a flow diagram illustrating the manufacture of a blastmedia composition representing still another alternate preferredembodiment of the present invention in which dense glass oxide or metaloxide particles are added;

[0040]FIG. 8 is a flow diagram illustrating the manufacture of a blastmedia composition representing an alternate preferred embodiment of thepresent invention in which dense particles are added in another way;

[0041]FIG. 9 is a schematic diagram showing the apparatus used in amethod for manufacturing a sanding pad incorporating another preferredembodiment of the present invention;

[0042]FIG. 10 is a photograph showing a perspective magnified view of asanding pad made with the apparatus shown in FIG. 9; and

[0043]FIG. 11 is a photograph showing a perspective magnified view of anano-sized montmorillomite clay polymer grade class particle used in theblast media of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] Referring to FIG. 1, the composite side of the composition isprepared by mixing a melamine compound with 35% alpha cellulose blendand compression molding the same at temperatures of a range of 280°F.-330° F. and pressures of 300 tons psi-500 tons psi (per square inch).The resulting composition is ground to 30/40 mesh size. Thenano-structure side is prepared by blending a urea compound with{fraction (1/2)}% nano-sized montmorillonite polymer grade clay. Thenano-structure additives may be varied from {fraction (1/2)}%-5%depending on application. This composition is compression molded at atemperature from 280° F.- 330° F. and at a pressure of 300 tons psi -500 tons psi. The resulting compression molded composition is ground to40/60 mesh size. The composite side in the nano-structure side are thenblended in a 1:1 proportion creating 30/60 mesh size. In the use ofcomposition manufactured in this way, a {fraction (1/2 )}inch doubleVenturi nozzle is employed using a flow rate of from 600 lbs.-1,000lbs./hr. at a 45° angle with a 15-18 inch standoff. For aerospaceapplications, pressure should not exceed 30 psi or for aluminum ALCLADpressure should be 25 psi and for bare aluminum pressure should be 30psi.

[0045] Referring to FIG. 2, the composite side in an alternateembodiment is a melamine compound with 35% alpha cellulose blend iscompression molded at a temperature of about 280° F.-330° F. and at apressure of from 300 tons psi -500 tons psi and then ground to 30/40mesh size.

[0046] The nano-structure side is prepared by blending a urea compoundby {fraction (1/2)}% by weight nano-size montmorillonite polymer gradeclay. This nano-structured additive can be varied from {fraction(1/2)}to 5% and is compression molded at a temperature of about 280°F.-330° F. and at a pressure of from 300 tons psi-500 tons psi and thencooled and ground to 40/60 mesh size.

[0047] An acrylic side is prepared by grinding to a 30/40 mesh size across-linked cast acrylic to 30/40 mesh size and blending the same atequal proportions with the composite and nano-structure side. Thiscomposition is used with a {fraction (1/2)}inch double Venturi nozzle ata flow rate of 600 lbs.-1000 lbs./hr, at a 45° -60° angle from thehorizontal.

[0048] The composition prepared in the above way is used with a{fraction (1/2)}inch double Venturi flow rate at from 600 lbs.-1,000lbs./hr at an angle of 45 degrees-60 degrees from the horizontal. Foraerospace applications 30 psi was not exceeded with 25 psi being used ataluminum ALCLAD and 30 psi on bare aluminum. For composites, pressureswere 15 psi-30 psi.

[0049] This media is particularly useful in the removal of aerospacecoatings from sensitive and thin substrates in which the safety of thesubstrate is an important concern. Again the nano-sized montmorilloniteclay is incorporated into the composite side and a third side ofcross-linked cast acrylic is added. The purpose of the cross-linkedacrylic is to lighten the specific gravity of the media thus loweringthe media weight affecting the surface upon impact under pressure. Thismedia also remains sharp as it fractures while downsizing in theblasting process. This media is safe on substrates that have been verydifficult to de-paint in the past such as KEVLAR composite polymer,lightning strike surfaces or very thin-skinned aluminum.

[0050] Referring to FIG. 3, the composite side in an alternateembodiment is a melamine compound with 35% alpha cellulose blend iscompression molded at a temperature of about 280° F.-330° F. and at apressure of from 300 tons psi -500 tons psi (per square inch) and thenground to 20/30 mesh size.

[0051] The nano-structure side is prepared by blending a urea compoundby {fraction (1/2)}% by weight nano-size montmorillonite polymer gradeclay. This nano-structured additive can be varied from 1% to 5% and iscompression molded at a temperature of about 280° F.-330° F. and at apressure of from 300 tons psi-500 tons psi and then cooled and ground to30/40 mesh size.

[0052] An acrylic side is prepared by grinding a cross-linked castacrylic to 20/30 mesh size and blending the same at equal proportionswith the composite and nano-structure side. This composition is usedwith a {fraction (1/2 )}inch double Venturi nozzle at a flow rate of 600lbs.-1000 lbs./hr, at a 45° -60° angle from the horizontal.

[0053] The composition prepared in the above way is used with a{fraction (1/2 )}inch double Venturi flow rate at from 600 lbs.-1,000lbs./hr at an angle of 45 degrees-60 degrees from the horizontal. Foraerospace applications 30 psi was not exceeded with 25 psi being used ataluminum ALCLAD and 30 psi on bare aluminum. For composites, pressureswere 15 psi-30 psi.

[0054] Referring to FIG. 4, the composite side is prepared by a blend ofa melamine compound with 65-35% alpha cellulose blend, which iscompression molded at a temperature about 280° F.-330° F. and at apressure of from 300 tons psi-500 tons psi (per square inch) and then to20/30 mesh size after cooling. The nano-structure side is prepared byblending a urea compound with {fraction (1/2)}% nano-size plusmontmorillonite polymer grade clay. The nano-structure additive can bevaried from {fraction (1/2)}% to 5%. The blend is compression moldedfrom about 280° F.-330° F. and at a pressure of from 300 tons psi-500tons psi. The nano-structure is ground into two separate portions, onebeing 16/20 mesh size and the other being 30/40 mesh size. Particles inthis blend are then mixed with a 1 % aqueous solution of a nonionicsurfactant. These particles are then mixed with a silane liquid polymercoupling agent. The mixture is then agitated and a pre-polymer urethaneto form a polyurethane coating on the particles. Further relevantinformation concerning the application of a polyurethane coating onparticles may be contained in U.S. Patent No. 5,405,648, the contents ofwhich are incorporated herein by reference.

[0055] Referring to FIG. 5, the composite side is prepared by a blend ofa melamine compound with 35% alpha cellulose blend, which is compressionmolded at a temperature about 280° F.-330° F. and at a pressure of from300 tons psi-500 tons psi and then to 20/30 mesh size after cooling. Thenano-structure side is prepared by blending a urea compound with{fraction (1/2)}% nano-size plus montmorillonite polymer grade clay. Thenano-structure additive can be varied from {fraction (1/2)}% to 5%depending on application. The blend is compression molded from about280° F.-330° F. and at a pressure of from 300 tons psi-500 tons psi (persquare inch). The nano-structure is ground into two separate portions,one being 16/20 mesh size and the other being 30/40 mesh size. Across-linked cast acrylic is ground to 30/40 mesh size. The compositeside 20/30 mesh, nano-structured side 30/40 mesh and acrylic side 30/40mesh are blended in equal parts creating a 20/40 mesh size. The 20/40mesh size is then blended in a 1:1 ratio with nano-structure side 16/20mesh size creating a 16/40 mesh size. This composition is preferablyused with a 3/8 inch double Venturi nozzle at a flow rate of 600lbs./hr. at an angle of 60°-80° from a horizontal. Ordinarily, pressuresgreater than 30 psi would not be used. This media is found to beparticularly adapted for fast and save removal of epoxy and polyurethanecoatings used on aircraft wheels.

[0056] Referring to FIG. 6, the composite side is prepared by a blend ofa melamine compound with 35% alpha cellulose blend, which is compressionmolded at a temperature about 280° F.- 330° F. and at a pressure of from300 tons psi-500 tons psi (per square inch) and then to 20/30 mesh sizeafter 48 hours cooling. Also blended with the composite side is a TypeIII melamine compound ground to 30/40 mesh size and a Type VIallyldiglycol carbonate is ground to 20/30 mesh size. The compositeside, Type III side, and Type VI side compositions are blended in equalamounts. The Type III and Type VI compositions are defined in MILSPEC85891A. The nano-structure side is prepared by blending a urea compoundwith {fraction (1/2)}% nano-size plus montmorillonite polymer gradeclay. The nano-structure additive can be varied from {fraction (1/2)}%to 5% depending on application. The blend is compression molded fromabout 280° F.-330° F. and at a pressure of from 300 tons psi-500 tonspsi (per square inch). The 20/40 mesh size blended composition is thenblended in a 1:1 ratio with the nano-structure side 10/20 mesh sizecreating a 10/40 mesh size composition. This composition is preferablyused with a 3/8 inch double Venturi nozzle at a flow rate of 600lbs./hr. at an angle of 80° from a horizontal. Ordinarily, pressuresgreater than 30 psi would not be used. This media is found to beparticularly adapted for fast and save removal of epoxy and polyurethanecoatings used on aircraft wheels.

[0057] The media described in connection with FIGS. 5 and 6 areparticularly useful for the fast and safe removal of aerospace coatingsused on aircraft wheels, landing gear and cast aluminum parts whereexposure to high heat has made coating removal very difficult. Thehardness of such coatings is elevated due to the extreme temperatureexposure. These coatings can be removed very quickly because of thenano-composite structure incorporated in this media. The protectiveanodized coating used on these parts is left totally intact due to thespeed of the de-paint process.

[0058] Referring to FIG. 7, a composite side of the media is a melaminecompound with a 50% alpha cellulose blend, which is compression moldedat temperatures from 280° F.-330° F. and 300 tons psi-500 tons psi (persquare 20 inch). The nano-structure side is a urea compounded blendedwith {fraction (1/2)}% by weight by nano-sized montmorillonite polymergrade clay. The nano-structure additive can be varied from {fraction(1/2)}%-5% depending on application and the nano-structure side iscompression molded at temperatures from 280° F.-330° F. at a pressure offrom 300 tons psi-500 tons psi (per square inch). The nano-structureside composition is cooled and ground to 40/60 mesh size. The compositeside and the nano-structure side are blended at a ratio of 1:1 creatinga 30/60 mesh size. Dense particle additives, which may be selected fromglass oxide cullet of a mesh size −80 or aluminum oxide of a grit size320. Either one of the dense particle additives are blended with the30/60 mesh size media at a rate of 20% by weight. The percentages of thedense particles may be very dependent upon a particular application.This media is preferably used with a {fraction (1/2)}inch double Venturinozzle at a flow rate of 600 lbs./hr.-1,000 lbs./hr at a 45 degree anglewith a {fraction (15/18 )}inch standoff. Ordinarily, pressures of 25 psion aerospace applications would not be exceeded. This media is found tobe well adapted for fast and safe removal of heavier epoxy andpolyurethane coatings used in the aerospace industry. Microfine denseparticle additives increase strip rate, decreasing dwell time on thesurface thus eliminating damage to sensitive substrates.

[0059] Referring to FIG. 8, a composite side of the media is a melaminecompound with a 35% alpha cellulose blend, which is compression moldedat temperatures from 280° F.-330° F. and pressures from 300 tons psi-500tons psi (per square inch). In this embodiment, the dense particleadditive, which could be glass oxide cullet of a −80 mesh size oraluminum oxide grit size 320 is added to the melamine and alphacellulose blend. The melamine and alpha cellulose blend is ground to30/40 mesh size and either of these dense particle additives are blendedin the amount of 20% weight although this amount may vary depending onapplication. The nano-structure side is a urea compound blended with{fraction (1/2)}% by weight by nano-sized montmorillonite polymer gradeclay. The nano-structure additive can be varied from {fraction(1/2)}%-5% depending on application. The nano-structure side compressionis molded at temperatures from 280° F.-330° F. at a pressure of from 300tons psi-500 tons psi (per square inch). The composition is cooled andground to 40/60 mesh size. The composite side and the nano-structureside are blended at a ratio of 1:1 creating a 30/60 mesh size. Thismedia is preferably used with a {fraction (1/2)}inch double Venturinozzle at a flow rate of 600 lbs./hr.-1,000 lbs./hr at a 45 degree anglewith a {fraction (15/18 )}inch standoff. Ordinarily, pressures of 25 psion aerospace applications would not be exceeded. This media is found tobe well adapted for fast and safe removal of heavier epoxy andpolyurethane coatings used in the aerospace industry. Microfine denseparticle additives increase strip rate, decreasing dwell time on thesurface thus eliminating damage to sensitive substrates.

[0060] The media described in connection with FIGS. 7 and 8 areparticularly useful for the fast and safe removal of extra heavy ormulti-layered coatings used in the aerospace industry. Micro-fine denseparticle additives are used to increase strip rates, decreasing dwelltime on the surface, thus eliminating damage or impinging stress onsensitive substrates. Again the use of nano-sized montmorillonite clayis essential to the polymer by increasing the durability of the polymerand eliminating rapid attrition due to the aggressive nature of thedense particle additives. The presence of the polymer with the denseparticle additive also behaves as a buffer not allowing the denseparticle additive to become too aggressive on the substrate. This mediais very effective on heavier coatings such as Radar Absorbent Material(RAM).

[0061] Referring to FIG. 9, a method and apparatus for making a sandingpad is shown. Aluminum oxide grit 10 is introduced to grit feeder 12 toa Acrison blender shown generally at numeral 14 which includes anIntrometer variable 15 speed mixer 16 and a metering auger 18. There isalso a polymer drum 20 which is equipped with a top heating band 22 anda bottom heating band 24. Nano-sized montmorillonite clay 26 isintroduced to drum blender 28 to polymer drum to form a polymer andnano-sized montmorillonite clay blend in the polymer drum 20 which isremoved by polymer pump 30 in line 32 to the Acrison blender 14. Theblended polymer is removed from the Acrison blender 14 in the meterauger 18 to vertical auger 34. A cellulose and water mixture is removedfrom container 36 by pump 38 in line 40 to extruder 42 to formingconveyor 44 where the cellulose and water mixture is mixed with thepolymer blend from vertical auger 34 and is then foam extruded from die46 onto continuous conveyor belt 48. At the end of the conveyor belt 48the extruded material 50 is cut by vertical knife 52 into segments as atsegment 54 which are stacked for cooling on pallet 56.

[0062] Referring to FIG. 10, a magnified photograph of the product ofthe method of making the sanding pad as described above is shown. Theresulting cellular structure of the sanding pad is illustrated withreference to the rule shown in which the marks shown are {fraction (1/8)}inch apart.

[0063] Referring to FIG. 11, a magnified photograph of a nano-sizedmontmorillonite polymer grade clay particle is shown. Such particles aregenerally platelet shaped. These particles have a major dimension whichwill generally be in the range of about 100 nm to almost 1,000 nm. Theseparticles also have a minor dimension which will generally be in therange of about 1 nm to about 20 nm.

[0064] It will be understood that other nano-sized additives and fillersmay be substituted for the nano-sized montmorillonite polymer grade clayin the practice of this invention. One such suitable nano-sized additiveare polyhedral oligomeric silsesquioxane additives which arecommercially available from Hybrid Plastics located at 18237 Mt. BaldyCircle, Fountain Valley, Calif. 92708-6117 USA.

[0065] In making the blast media as described above, it will beunderstood that other thermoplastic polymers may be substituted for themelamine. For example, suitable thermosetting polymers include ureaformaldehyde, phenal formaldehyde, polyester, polyurethane, and epoxy.

[0066] the methods and compositions of the present invention are furtherillustrated by the following examples.

EXAMPLES

[0067] EXAMPLE 1

[0068] (FIG. 1)

[0069] The powdered melamine compound commercially available fromBritish Industrial Plastics (BIP) under tradename/product number MelmexMFB 10/B11 was blended with 65.35 by weight alpha cellulose which iscommercially available from J. Rettenmaier USA LP (JRS) undertradename/product number ARBOCEL/BWW40 and compression molded at atemperature of 300° F. at a pressure of 500 tons psi. The resultingmixture was allowed to cool for 1 Day and was then ground in a ReductionEngineering disc mill grinder to a 30/40 mesh size. Separately a ureacompound commercially available from BIP under tradename/product numberBeetle GXT UF A-10 in the amount of 1,000 grams was blended by weightwith nano-sized montmorillonite polymer grade clay commerciallyavailable from Nanocor, Inc. under tradename/product number PolymerGrade Montmorillonite Nanomer PGV in the amount of 10 grams. Theresulting blend was compression molded at a temperature of 300° F. and apressure of 500 tons psi in a hydraulic compression molding press. Theblend was allowed to cool for 1 day and was then ground to a 40/60 meshsize. 1,000 grams of the composite side component described above wasmixed with 1,000 grams of the nano-structure side.

[0070] EXAMPLE 2

[0071] (FIG. 2)

[0072] The powdered melamine compound commercially availabe from BIPunder tradename/product number Melmex MF B10/B11 was blended with 65/35by weight alpha cellulose which is commercially available from JRS undertradename/product number Arbocel/BWW40 and compression molded at atemperature of 300° F. at a pressure of 500 tons psi. The resultingmixture is allowed to cool for 1 day and was then ground in a ReductionEngineering disc mill grinder to a 30/40 mesh size. Separately a ureacompound commercially available from BIP under tradename/product numberBeetle GXT UF A-10 in the amount of 1,000 grams was blended by weightwith nano-sized montmorillonite polymer grade clay commerciallyavailable from Nanocor, Inc. under tradename/product number Nanomer PGVin the amount of 10 grams. The resulting blend was compression molded ata temperature of 300° F. and a pressure of 500 tons psi in a hydrauliccompression molding press. The blend was allowed to cool for 1 day andwas then ground to a 40/60 mesh size. 1,000 grams of the composite sidecomponent described above was mixed with 1,000 grams of thenano-structure side. A cross-linked cast acrylic commercially availablefrom Aristech Corp. under the tradename/product number Acrylic I-300 wasground 30/40 mesh size and blended at equal proportion with thecomposite and nano-structure side.

[0073] EXAMPLE 3

[0074] (FIG. 3)

[0075] The powdered melamine compound commercially available from BIPunder tradename/product number Melmex MF B10/B11 was blended with 65/35by weight alpha cellulose which is commercially available from JRS undertradename/product number Arbocel/BWW40 and compression molded at atemperature of 300° F. at a pressure of 500 tons psi. The resultingmixture is allowed to cool for 1 day and was then ground in a ReductionEngineering disc mill grinder to a 20/30 mesh size. Separately, a ureacompound commercially 20 available from BIP under tradename/productnumber Beetle GXT UF A-10 in the amount of 1,000 grams was blended byweight with nano-sized montmorillonite polymer grade clay commerciallyavailable from Nanocor, Inc. under tradename/product number Nanomer PGVin the amount of 10 grams. The resulting blend was compression molded ata temperature of 300° F. and a pressure of 500 tons psi in a hydrauliccompression molding press. The blend was allowed to cool for 1 day andwas then ground to a 40/60 mesh size. 1,000 grams of the composite sidecomponent described above was mixed with 1,000 grams of thenano-structure side. A cross linked cast acrylic commercially availablefrom Aristech Corp. under the tradename/product number Acrylic I-300 wasground 30/40 mesh size and blended at equal proportion with thecomposite and nano-structure side.

[0076] EXAMPLE 4

[0077] (FIG. 4)

[0078] The powdered melamine compound commercially available from BIPunder tradename/product number Melmex MF B10/B 11 is blended with 65-35%by weight alpha cellulose which is commercially available from BIP undertradename/product number Beetle GXT UF A-10 in the amount of 1,000 gramsis blended by weight with nano-sized montmorillonite polyer grade claycommercially available from Nanocor, Inc. under tradename/product numberNanomer PGV in the amount of 10 grams. The resulting blend iscompression molded at a temperature of 300° F. and a pressure of 500tons pi in a hydraulic compression molding press. The blend is allowedto cool for 1 day and was then ground to a 40/60 mesh size. 1,000 gramsof the composite side component described above was mixed with 1,0000grams of the nano-structure side. A cross-linked cast acryliccommercially available from Aristech Corp. under the tradename/productnumber Acrylic I-300 is ground 30/40 mesh size and blended at an equalproportion with the composite and nano-structure side. Grams ofparticles in this blend were then introduced to a tank which was thenfilled with a water surfactant mixture. The surfactant is a non-ionicsurfactant commercially available from the B.A.S.F. Company under thetradename/product number F88. The surfactant is used in a 1 % by weightconcentration in water. The particles are then agitated. The water isthen removed and the particles are treated with a silane liquid polymercoupling agent available. The mixture is then agitated and a liquidpre-polymer urethane available from Blend Manufacturing, Inc. ofSomersworth, N.H. USA under the tradename/product number MATRIX wasadded. The ratio by weight of the silane coupling agent to the urethanepre-polymer is 1:10.07. The resulting film on the particles is allowedto dry.

[0079] EXAMPLE 5

[0080] (FIG. 5)

[0081] The powdered melamine compound commercially available from BIPunder tradename/product number Melmex MF B10/B11 was blended with 65-35by weight alpha cellulose which is commercially available from JRS undertradename/product number Arbocell/BWW40 and compression molded at atemperature of 300° F. at a pressure of 500 tons psi. The resultingmixture was allowed to cool for 1 day and was then ground in a ReductionEngineering Disc mill grinder to a 20/30 mesh size. Separately, a ureacompound commercially available from BIP under tradename/product numberBeetle GXT UF A-10 in the amount of 1,000 grams was blended by weightwith nano-sized montmorillonite polymer grade clay commerciallyavailable from Nanocor, Inc. under tradename/product number Nanomer PGVin the amount of 10 grams. The resulting blend was compression molded ata temperature of 300° F. and a pressure of 500 tons psi in a Hydrauliccompression molding press. The blend was allowed to cool for 1 day andwas then ground to 16/30 and 30/40 mesh size. A cross-linked castacrylic commercially available from Aristech Corp. under thetradename/product number Acrylic I-300 was ground to 30/40 mesh size.The composite side 20/30 mesh, nano-structure side 30/40 mesh andacrylic side 30/40 mesh size were blended in 1:1 ratio withnano-structure side 16/20 mesh size creating a 16/40 mesh size.

[0082] EXAMPLE 6

[0083] (FIG. 7)

[0084] The powdered melamine compound commercially available from BIPunder tradename/product number Melmex MF B10/B11 was blended in a ratioas 65-35% by weight with alpha cellulose which is commercially availablefrom JRS under tradename/product number Arbocel/BWW40 and compressionmolded at a temperature of 300° F. at a pressure of 500 tons psi. Theresulting mixture was allowed to cool for 1 day and was then ground in aReduction Engineering disc mill grinder to a 30/40 mesh size.Separately, a urea compound commercially available from BIP undertradename/product number Beetle GXT UF A-10 was added in the amount of1,000 grams was blended by weight with a nano-sized montmorillonitepolymer grade clay commercially available from Nanocor, Inc. undertradename/product number Nanomer PGV in the amount of 10 grams. Theresulting blend was compression molded at a temperature of 300° F. and apressure of 500 tons psi in a hydraulic compression molding press. Theblend was allowed to cool for 1 day and was then ground to a 40/60 meshsize. The composite side and the nano-structure side were blended in a1:1 ratio creating a 30/60 mesh size blend to which a glass oxide culletor alox commercially available from alox—Strategic Materials, Inc. andglass frit-Exolong-ESK Company Glass under tradename/product numbersalox -320 grit and glass frit-80-was added in the amount of 20% byweight.

[0085] EXAMPLE 7

[0086] (FIG. 8)

[0087] A toluene diisocynanate based urethane liquid polymer which wascommercially obtained from Polyurethane Specialties Co. undertradename/product number PMS 1065 was placed in a polymer 55 gal. drumin the amount of 55 gals. Two heater bands were attached to the polymerdrum, one on the top and one on the bottom, and the polymer was heatedfor 1 hour to reach a temperature in the range of 95° -100° F.Nano-sized montmorillonite clay was commercially obtained from Nanocor,Inc. under tradename Nanomer and product number PVG was added to thepolymer at a rate of {fraction (1/2)}% by weight or 2.25 lbs./450 lb.drum. A Sharpe {fraction (1/2)}HP drum blender was used for 1 hour toblend the Nanomer and the polymer for 1 hour. After the first drumreached the desired temperature, a second drum was heated and blendedwith Nanomer in the same way. The polymer and Nanomer blend was thenpumped to Acrison mixer model no. 4048D021 volumetric feedermanufactured by Ronco at a rate of 8.5-9 lbs./min. by a Moyno pump modelno. 1000. 2,200 lbs. of 320 grit aluminum oxide were added to a gritfeed at a rate of 38 Ibs./min. The Acrison mixer contained a meter augerand an Intromiter mixer. A 3 in. variable speed metering auger moves theblended polymer and aluminum oxide from the Acrison to a vertical auger.A mixture of water and Technocell 200 cellulose which is 8.5% by weightcellulose and 91.5% by weight water is extruded in a 6 in. auger withmixing pins to feed water and cellulose into the polymer blend in theextruder at the rate of 1.83 lb./min. The cellulose and polymer blend isthen fed into a forming die having dimensions of 6″×4″×2″. The materialextruded from the die is fed to a conveyor belt where it is formed intoa continuous sheet 2 ft. wide and {fraction (1/2 )}in. thick. Thematerial sets up while on the conveyor for a period of 10 mins. At theend of the conveyor the material was cut into 4 ft. lengths and stackedonto a pallet where it was cured for 48 hrs. at a temperature of 65° F.After this cure period, the material was cut to dimensions of 6″×8″andthen packaged. A magnified photograph showing the cellular structure ofthe resulting pad is shown in FIG. 10. The resulting pad had a bulkdensity of 45 lbs./ft.³.

COMPARATIVE TESTS

[0088] Various tests were conducted to compare characteristics of thecomposite abrasives made in Examples 1, 2, and 3 with the prior art TypeI, II, III, V, X, and VII plastic blast mediums shown in Table 1 whichare commercially available from U.S. Technology Corporation located at220 7^(th) St. SE Canton, Ohio 44702 and which are defined in MILSPEC85891A. TABLE 1 Type Description Type I: a polyester compound Type II: aurea-formaldehyde compound with cellulose filler Type III: a polymerizedmelamine molding with alpha cellulose filler Type V: an acrylic compoundType VII: a starchgrafted acrylic compound Type X: a cross linkedacrylic compound

Breakdown Rate

[0089] A comparison of the breakdown rates of the commercially availableblast media was made with that of the new media as prepared by Examples1-3.

[0090] The particle size distribution of each of the blast media wasdetermined before and after blasting and the results summarized in Table2. The breakdown rates were calculated on both the commercial particlesize distribution and on the 80 mesh screen.

[0091] The breakdown rate was determined by using a blast cabinet.3′×3′×4′(wXhXd) without the vacuum return. At the bottom of the blastcabinet was a clap, which when opened, allowed all of the contents ofthe blast cabinet to be drained. The pressure pot, 1 cubic foot, wasequipped with 2 glass view ports to verify that all of the media hadbeen consumed. The air feed line was 1″I.D., and the media flow valvewas of the guillotine type. Over the pressure pot was a hopper withoutscreens. The media was manually poured into the pressure pot via thehopper. The blast hose was 1″I.D., and about 8′long. The nozzle was{fraction (1/4 )}straight barrel.

[0092] An aluminum plate was placed at 10 inches and 80° to the blastnozzle. The pressure at the nozzle was measured by inserting the needlegauge into the rubber hose directly behind the nozzle such that theneedle was in the direction of the air flow. The media flow rate wasmeasured by timing the consumption of 10 lbs. of abrasive media at thedesired nozzle pressure. The particle size of the unblasted media wasdetermined as was that of the media after 4 blast cycles.

[0093] The breakdown rate was calculated to military specificationMIL-P-85891AS. the particle size distribution of Example 1 was narrow inthe ground media as seen in Table 2. About 78% of the media was on the30, 40, and 50 mesh screens. After 4 cycles, the mean particle sizeshifted by one screen. About 92% was on the 40, 50, 60, and 80 meshscreens. The breakdown rate of Example 5 compared favorably to thebreakdown rates of 13% in the pro. The highest breakdown rate is that ofwheat starch blast media at 15% and the lowest is Example 2 at 4%.

[0094] Comparisons based solely on the new media size can be deceivingsince most blast equipment only separates particles finer than 80 meshfrom the blast medium. Based on breakdown below 80 mesh, the 4.4%breakdown of Example 2 compares favorably to the other media. Thehighest breakdown rate being 1, 3, and 7 at 15% and the lowest beingExample 2 at 4%. The other media have breakdown rates of about 6-13%.

Almen Arc Height

[0095] In measuring the almen arc height, a block capable of holding 3almen strips was used. Clad aluminum, 0.032″thick almen strips were usedwith a digital almen gauge. The pressure at the nozzle was measured byinserting a needle gauge into the rubber hose directly behind the nozzlesuch that the needle was in the direction of the air flow. The mediaflow rate was measured by timing the consumption of 10 lbs. of abrasivemedia at the desired nozzle pressure. The arc of 3 unused almen stripswas measured and recorded. The strips were placed into the block andsecured without over tightening the holding screws.

[0096] For the single pass almen arc height, the following procedure wasused. Immediately following the coating removal rate test and withoutinterruption, the almen block containing 3 almen strips was exposed tothe blast using the same motion and technique used to remove thecoating. The almen strips were removed form the block, wiped clean witha dry cloth and the arc remeasured and recorded.

[0097] For the saturation almen arc height, the almen block was blastedfor 10 seconds at the preset pressure and media flow rate, at7″stand-off and at 70°-85° impingement angle. The arc of each almenstrip was measured and the almen strips were replaced in the block.These steps were repeated until no further significant change in almenarc was recorded.

[0098] Almen arc height is a measure of the residual stresses afterblasting. The shot peening effect is detrimental to most aircraft skins.Therefore, the lower the almen arc height the better. Table 2 is acomparison of the almen arc heights of Examples 1-3 with various priorart compositions. Examples 1-3 of the present invention compared veryfavorably with the softer prior art compositions.

[0099] Almen strips were made form 2024-T3 clad aluminum.

Coating Removal Rate

[0100] The coating removal rate was determined using a blast cabinet,540×3′×5′(wXhXd), with vacuum return. At the bottom of the cyclone was ahopper with a clap, which when opened allowed all of the contents of thehopper to be drained. During blasting, the media and dust were separatedin the cyclone. The media was collected in the hopper and the dust wascollected in the bag house. Over the pressure pot 3 cubic feet, was ahopper without screens. The media was manually filled into the hopper.The air feed line was 1′I.D., and the media flow valve was of theguillotine type. Over the pressure pot was a hopper without screens. Themedia was manually poured into the pressure pot via the hopper. Theblast hose was 1″I.D. and about 8+long. The nozzle was {fraction(1/4″)}straight barrel.

[0101] Panels with mil-C-83286 top coat and mil-P-23377 primer wereused. The pressure at the nozzle was measured by inserting the needlegauge into the rubber hose directly behind the nozzle such that theneedle was in the direction of the air flow. The media flow rate wasdetermined by timing the consumption of 10 lbs. of abrasive media at thedesired nozzle pressure. Maintaining the nozzle at 10″ and at an 80°angle, the paint was removed to the bare metal. As much paint as couldbe removed completely within one minute was removed. Without stopping,the single pass almen height samples were blasted. Both the surface areaof paint removed as well as the exact time required to remove the paintwas recorded in Table 2.

[0102] All coating removal rate tests were performed using a {fraction(1/4 )}inch diameter nozzle. This is smaller than the nozzles used toremove coatings from aircraft parts and components. Since the coatingremoval rate is dependent on the surface area of the nozzle, all otherparameters remaining constant, the coating removal rate will increase bya factor of 4 when the nozzle diameter is doubled.

[0103] The coating removal rate of the humidified media did not change,indicating that the media is stable when stored under 95% R.H. at 33° C.conditions. This is significant in that coating removal rate isgenerally the most sensitive property to water uptake. The almen archeight and hardness values will decrease, but the coating removal ratedecreases before any changes in hardness or almen arc height areobserved. Since none of the properties changed after 36 hours to highhumidity conditions, the blast properties of the media are stable undermost environmental conditions.

Surface Roughness

[0104] The following are the surface roughness measurements which wereobtained from panels on which the coating removal rate test wasperformed at 35 psi as shown in Table 2.

[0105] The RA average surface roughness of clad aluminum panels strippedusing Examples 1-3 are shown. This compared favorably with the prior artcompositions. Since the surface roughness is so low, the cladding isdisturbed the least with Examples 1-3 than with the other prior artmedia. Also, since clad can be repolished after the paint was stripped,it should also be possible to repolish the clad substrate afterstripping paint with Examples 1-3.

Water Uptake Rate

[0106] In order to measure the water uptake rate of various blast media,a glass indicator was used as a humidity chamber. A watch glass was usedto expose the media to the environment inside the desiccator. Potassiumsulfate (K₂SO₄) was used to maintain the humidity within the desiccator.A 25 g. sample of the media was weighted and placed into a porcelainevaporating dish and placed in the desiccator for 13 hours, after whichthe media was removed and reweighed.

TEST SERIES 2

[0107] The tests described with respect to Test Series 1 above wererepeated on the blast media shown in Table 3. Somewhat different testconditions were also used which are shown in Table 3. The results ofthese tests are also shown in Table 3.

[0108] It will be appreciated that a polymeric blast media has beendescribed which efficiently and cost effectively removes organiccoatings from substrates.

[0109] It will also be appreciated that polymeric blast media has beendescribed which allows removal of organic coatings from substrates.

[0110] It will also be appreciated that a polymeric blast media can beused to remove standard abrasive organic coatings without substantialrisk of damage to sensitive metal or composite substrates.

[0111] It will also be appreciated that a polymeric blast media has beendescribed which has a high degree of durability.

[0112] It will also be appreciated that a polymeric blast media has beendescribed which has favorable surface roughness, almen arc height, andwater absorbence characteristics.

[0113] While the present invention has been described in connection withthe preferred embodiments of the various figures, it is to be understoodthat other similar embodiments may be used or modifications andadditions may be made to the described embodiment for performing thesame function of the present invention without deviating therefrom.Therefore, the present invention should not be limited to any singleembodiment, but rather construed in breadth and scope in accordance withthe recitation of the appended claims. TABLE 2 EXAMPLE EXAMPLE EXAMPLEType I Type II Type III Type V Type X Type VII 1 2 3 Hardness 34-4254-62 64-72 46-54 46-54 73-77 54-60 54-60 54-60 Barcol Barcol BarcolBarcol Barcol Shore D Barcol Barcol Barcol Ignition Temp 440-C. >530-C.390-C. 390-C. 365-C. >530-C. >530-C. >530-C. Chlorine Content TraceTrace Trace Trace Trace Trace Trace Trace Trace Ash Content 1.0% by wt2.0% by wt 2.0% by wt 0.5% by wt 0.5% by wt 1.0% by wt 2.0% by wt 2.0%by wt 2.0% by wt Iron Content 0.05% by wt 0.10% by wt 0.10% by wt 0.05%by wt 0.05% by wt 0.05% by wt 0.10% by wt 0.10% by wt 0.10% by wtSpecific Gravity 1.15-1.25 1.476-1.52 1.47-1.52 1.10-1.20 1.10-1.201.38-1.43 1.40-1.46 1.36-1.46 1.36-1.46 Extract Content 5.0% by wt 1.0%by wt 1.0% by wt 95% min 95% min 10.0% by wt 1.0% by wt 95% min 95% minPh 4 to 8 4 to 8 4 to 8 4 to 8 4 to 8 4 to 8 4 to 8 4 to 8 4 to 8Conductivity 100 mho/cm 100 mho/cm 100 mho/cm 100 mho/cm 100 mho/cm 100mho/cm 100 mho/cm 100 mho/cm 100 mho/cm H2O Absorbance 2.0% by wt 10.0%by wt 10.0% by wt 2.0% by wt 2.0% by wt 15.0% by wt 10.0% by wt 10.0% bywt 10.0% by wt Heavy Particle 0.02% by wt 0.02% by wt 0.02% by wt 0.02%by wt 0.02% by wt 0.02% by wt 0.02% by wt 0.02% by wt 0.02% by wt LightParticle 1.0% by wt 1.0% by wt 1.0% by wt 0.1% by wt 0.1% by wt 1.0% bywt 1.0% by wt 1.0% by wt 1.0% by wt Surf. Roughness 0.2 mg/sq 0.31 mg/sq3.0 mg/sq 9.35 um/.2 0.75 mg/sq .093 um/10 200 u Inches 200 u inches 200u inches cm cm mg/sq cm cm mg/sq cm max max max Almen Arc 0.0016 0.00910.0065 0.0038 0.0032 0.0026 0.0054 0.0033 0.0061 inches inches inchesinches inches inches inches inches inches Blast Pressure 50 psi 25 psi25 psi 30 psi 30 psi 35 psi 30 psi 25 psi 25 psi Consumption 15%/cycle13%/cycle 15%/cycle 6%/cycle 5%/cycle 15%/cycle 5%/cycle 4%/cycle5%/cycle Flow Rate lbs/hr 215-245 lbs/ 140-170 lbs/ 125-155 lbs/ 140-170lbs/ 140-170 lbs/ 540-600 lbs/ 500-720 lbs/ 500-720 lbs/ 600-720 lbs/ hrhr hr hr hr hr hr hr hr Strip rate per - ¼″ - .19 ¼″ - .33 ¼″ - .38{fraction (12/4)}″ - .223 ¼″ - .183 ¼″ - 0.194 ¼″ - .65 ¼″ - 0.26 ¼″ -0.4125 sq ft/min sq ft/min sq ft/min sq ft/min sq ft/min sq ft/min sqft/min sq ft/min sq ft/min Nozzle Size {fraction (3/6)}″ - .38 ⅜″ - .66⅜″ - .76 ⅜″ - .459 {fraction (3/6)}″ - .367 ⅜″ - 0.368 ⅜″ - 2.6{fraction (7/16)}″ - 1.025 {fraction (7/16)}″ - 1.85 sq ft/min sq ft/minsq ft/min sq ft/min sq ft/min sq ft/min sq ft/min sq ft/min sq ft/min{fraction (7/16)} - .76 {fraction (7/16)} - 1.3 {fraction (7/16)} - 1.5{fraction (7/16)}″ - .919 {fraction (7/16)}″ - .73 {fraction (7/16)}″ -0.777 {fraction (7/16)}″ - 2.6 {fraction (7/16)}″ - 1.025 {fraction(7/16)}″ - 1.85 sq ft/min sq ft/min sq ft/min sq ft/min sq ft/min sqft/min sq ft/min sq ft/min sq ft/min ½″ - 1.5 ½″ - 2.6 ½″ - 3.0 ½″ -1.63 ½″ - 1.94 ½″ - 1.55 ½″ - 5.2 ½″ - 2.05 ½″ - 3.3 sq ft/min sq ft/minsq ft/min sq ft/min sq ft/min sq ft/min sq ft/min sq ft/min sq ft/min

[0114] TABLE 3 Type I Type II Type III Type V Type VII 2050 EXAMPLE 1EXAMPLE 2 Hardness 34-42 Barcol 54-62 Barcol 64-72 Barcol 46-54 Barcol73-77 Shore D 54-60 Barcol 54-60 Barcol Ignition Temp 440-C.530-C. >530-C. 390-C. 365-C. >530-C. >530-C. Chlorine Content TraceTrace Trace Trace Trace Trace Trace Ash Content 1.0% by wt 2.0% by wt2.0% by wt 0.5% by wt 1.0% by wt 2.0% by wt 2.0% by wt Iron Content0.05% by wt 0.10% by wt 0.10% by wt 0,05% by wt 0.05% by wt 0.10% by wt0.10% by wt Specific Gravity 1.15-1.25 1.47-1.52 1.47-1.52 1.10-1.201.38-1.43 1.40-1.46 1.36-1.46 Extract Content 5.0% by wt 1.0% by wt 1.0%by wt 95% min 10.0% by wt 1.0% by wt 95% min Ph 4108 4 to 8 4 to 8 4 to8 4 to 8 4 to 8 4 to 8 Conductivity 100 mho/cm 100 mho/cm 100 mho/cm 100mho/cm 100 mho/cm 100 mho/cm 100 mho/cm H2O Absorbance 2.0% by wt 10.0%by wt 10.0% by wt 2.0% by wt 15.0% by wt 10.0% by wt 10.0% by wt HeavyParticle 0.02% by wt 0.02% by wt 0.02% by wt 0.02% by wt 0.02% by wt0.02% by wt 0.02% by wt Light Particle 1.0% by wt 1.0% by wt 1.0% by wt0.1% by wt 1.0% by wt 1.0% by wt 1.0% by wt Surf. Roughness 0.2 mg/sq cm0.31 mg/sq cm 3.0 mg/sq cm 9.35 um/.2 mg/ .093 um/10 200 u inches 200 uinches mg/sq cm sq cm max max Almen Arc 0.0016 inches 0.0091 inches0.0065 inches 0.0038 inches 0.0026 inches 0.0054 inches 0.0033 inchesBlast Pressure 50 psi 25 psi 25 psi 30 psi 35 psi 30 psi 30 psiConsumption 15%/cycle 13%/cycle 15%/cycle 6%/cycle 15%/cycle 5%/cycle4%/cycle Flow Rate lbs/hr 215-245 lbs/hr 140-170 lbs/hr 125-155 lbs/hr140-170 lbs/hr 540-600 lbs/hr 600-720 lbs/hr 600-720 lbs/hr Strip Rateper - ¼″ - .19 sq ¼″ - .33 sq ¼″ - .38 sq ¼″ - .229 sq ¼″ 0.194 sq ¼″ -0.65 sq ¼″ - 0.46 sq ft/min ft/min ft/min ft/min ft/min ft/min ft/minNozzle Size ⅜″ - .38 sq ⅜″ - .66 sq ⅜″ - .76 sq ⅜″ - .459 sq ⅜″ - 0.388sq ⅜″ - 1.3 sq ⅜″ - 0.90 sq ft/min ft/min ft/min ft/min ft/min ft/minft/min {fraction (7/16)} - .76 sq {fraction (7/16)} - 1.3 sq {fraction(7/16)} - 1.5 sq {fraction (7/16)}″ - .919 sq {fraction (7/16)}″ - 0.777sq {fraction (7/16)}″ - 2.6 sq {fraction (7/16)}″ - 1.85 sq ft/minft/min ft/min ft/min ft/min ft/min ft/min ½″ - 1.5 sq ½″ -2.6 sq ½″ -3.0 sq ½″ - 1.83 sq ½″ - 1.55 sq ½″ - 5.2 sq ½″ - 3.95 sq ft/min ft/minft/min ft/min ft/min ft/min ft/min

What is claimed is:
 1. A method for making a polymeric blast mediacomprising the steps of: (a) blending a melamine compound with acellulosic material and compression molding said first blend to producea compression molded first blend, to produce a first blend and thencooling said first blend to produce a cooled first blend, and themgrinding said cooled first blend to produce a particulate first blend;(b) blending a urea compound with a nano-clay material to produce asecond blend and compression molding said second blend to produce acompression molded second blend, and then cooling said molded secondblend to produce a cooled second blend, and then grinding said cooledsecond blend to produce a particulate second blend; (c) blending theparticulate first blend with the particulate second blend.
 2. The methodof claim 1 wherein in step (a) the cellulosic material is alphacellulose.
 3. The method of claim 1 wherein in step (a) the first blendis compression molded at a temperature of from about 280° F. to about330° F. and under a pressure of from about 300 tons per square inch toabout 500 tons per square inch.
 4. The method of claim 1 wherein in step(a) the cooled first blend is ground to from about 20/30 mesh to about30/40 mesh.
 5. The method of claim 1 wherein in step (b) the nano-clayis montmorillonite.
 6. The method of claim 1 wherein in step (b) thesecond blend is compression molded at a temperature of from about 280°F. to about 330° F. and under a pressure of from about 300 tons persquare inch to about 500 tons per square inch.
 7. The method of claim Iwherein in step (a) the cooled first blend is ground to fromabout a20/30 mesh to about a 30/40 mesh particulate size.
 8. The method ofclaim 1 wherein in step (c) the first blend and second blend are blendedin a ratio of about 1:1 by weight.
 9. The method of claim 1 wherein instep (c) the third blend has a mesh particulate size from about 10/40mesh to about 30/60 mesh.
 10. The method of claim 1 wherein an acrylicpolymer is ground and then added to the blend in step (c).
 11. Themethod of claim 1 wherein the acrylic polymer is a cross-linked castpolymer.
 12. The method of claim 10 wherein the acrylic polymer isground to from about a 20/30 mesh size to about a 30/40 mesh size. 13.The method of claim 10 wherein the acrylic polymer is blended in aboutequal proportion with the first blend and the second blend.
 14. Themethod of claim 1 wherein in step (b) the second blend is ground to fromabout a 16/20 mesh size to about a 40/60 mesh size.
 15. The method ofclaim 11 wherein the first blend, the second blend and the groundacrylic are blended in equal parts in step (c).
 16. The method of claim1 wherein after step (c) wherein the blast media is comprised of aplurality of individual particles which a polyurethane coating isapplied.
 17. The method of claim 1 wherein a dense particulate materialselected from a glass oxide and a metal oxide is added to the blastmedia.
 18. The method of claim 17 wherein the dense particulate materialis a glass oxide material having a size of at least about −80 mesh. 19.The method of claim 17 wherein an aluminum oxide material having a gritsize of from about 230 to
 320. 20. The method of claim 1 wherein anabout 30/40 mesh size melamine compound material and an about 20/30 meshsize allyldiglycol carbonate material are added to the first blend. 21.A product of a method of making a polymeric blast media comprising thesteps of: (a) blending a melamine compound with a cellulosic materialand compression molding said first blend to produce a compression moldedfirst blend, to produce a first blend and then cooling said first blendto produce a cooled first blend, and then grinding said cooled firstblend to produce a particulate first blend; (b) blending a urea compoundwith a nano-clay material to produce a second blend and compressionmolding said second blend to produce a compression molded second blend,and then cooling said molded second blend to produce a cooled secondblend, and then grinding said cooled second blend to produce aparticulate second blend; (c) blending the particulate first blend withthe particulate second blend.
 22. The product of the method of claim 21wherein in step (a) the cellulosic material is alpha cellulose.
 23. Theproduct of the method of claim 21 wherein in step (a) the first blend iscompression molded at a temperature of from about 280° F. to about 330°F. and under a pressure of from about 300 tons per square inch to about500 tons per square inch.
 24. The product of the method of claim 21wherein in step (a) the cooled first blend is ground to from about 20/30mesh to about 30/40 mesh.
 25. The product of the method of claim 21wherein in step (b) the nano-clay is montmorillonite.
 26. The product ofthe method of claim 21 wherein in step (b) the second blend iscompression molded at a temperature of from about 280° F. to about 330°F. and under a pressure of from about 300 tons per square inch to about500 tons per square inch.
 27. The product of the method of claim 21wherein in step (a) the cooled first blend is ground to fromabout a20/30 mesh to about a 30/40 mesh particulate size.
 28. The product ofthe method of claim 21 wherein in step (c) the first blend and secondblend are blended in a ratio of about 1:1 by weight.
 29. The product ofthe method of claim 21 wherein in step (c) the third blend has a meshparticulate size from about 10/40 to about 30/60.
 30. The product of themethod of claim 21 wherein an acrylic polymer is ground and then addedto the blend in step (c).
 31. The product of the method of claim 32wherein the acrylic polymer is a cross-linked cast polymer.
 32. Theproduct of the method of claim 30 wherein the acrylic polymer is groundto from about a 20/30 mesh size to about a 30/40 mesh size.
 33. Theproduct of the method of claim 30 wherein the acrylic polymer is blendedin about equal proportions with the first blend and the second blend.34. The product of the method of claim 34 wherein in step (b) the secondblend is ground to from about a 16/20 mesh size to about a 40/60 meshsize.
 35. The product of the method of claim 35 wherein the first blend,the second blend and the ground acrylic are blended in equal parts instep (c).
 36. The product of the method of claim 36 wherein after step(c) wherein the blast media is comprised of a plurality of individualparticles which a polyurethane coating is applied.
 37. The product ofthe method of claim 37 wherein a dense particulate material selectedfrom a glass oxide and a metal oxide is added to the blast media. 38.The product of the method of claim 21 wherein the dense particulatematerial is a glass oxide material having a size of at least about −80mesh.
 39. The product of the method of claim 21 wherein an aluminumoxide material having a grit size of from about 230 to
 320. 40. Theproduct of the method of claim 21 wherein an about 30/40 mesh sizemelamine compound material and an about 20/30 mesh size allyldiglycolcarbonate material are added to the first blend.
 41. An abrasive mediafor the removal of coating or for the preparation of surfaces prior tocoating or cleaning comprising: a particulate thermosetting polymerwithan additive wherein said additive has a major dimension and a minordimension and said minor dimension is from about 1 nm to about 20 nm.42. The abrasive media of claim 1 wherein the minor dimension is about1.0 nm.
 43. The abrasive media of claim 41 wherein the additive is anano-clay material.
 44. The abrasive media of claim 43 wherein thenano-clay material is a montmorillonite clay.
 45. The abrasive media ofclaim 41 wherein the filler component is a polyhedral oligomericsilsesquioxane material.
 46. The abrasive material of claim 41 whereinthe major dimension of the additive is from about 100 nm to about 1,000nm.
 47. The abrasive media of claim 41 wherein the additive has aplatelet shape.
 48. The abrasive media of claim 41 wherein thethermosetting polymer is selected from one or more of the groupconsisting of urea formaldehyde, melamine formaldehyde, phenolformaldehyde, polyester, polyurethane, and epoxy.
 49. The abrasive mediaof claim 41 wherein the particulate thermosetting polymer is blendedwith a cellulosic material.
 50. The abrasive material of claim 41wherein the particulate thermosetting polymer is blended with a ureamaterial.
 51. A method of making a sanding pad for removing an organiccoating from a substrate comprising the steps of: (a) blending a liquidpolymeric material with a nano-clay material to produce a first blend;(b) blending a cellulosic material with said first blend to produce asecond blend; and (c) extruding the second blend to form a continuoussheet of abrasive material into a plurality of individual pads.
 52. Themethod of claim 51 wherein after step (c) the continuous sheet ofabrasive material is cut into a plurality of pads.
 53. The method ofclaim 52 wherein in step (a) an abrasive material is added to the firstblend.
 54. The method of claim 53 wherein the abrasive material isaluminum oxide.
 55. The method of claim 51 wherein in step (a) thenano-clay is montmorillonite.
 56. The method of claim 51 wherein in step(a) the polymeric material is a polyurethane.
 57. The method of claim 51wherein the cellulosic material is alpha cellulose.
 58. The method ofclaim 51 wherein in step (c) the second blend is foam extruded.
 59. Themethod of claim 51 wherein in step (a) the polymeric material is heated.60. The method of claim 52 wherein the abrasive material is added beforethe cellulosic material is added.
 61. A product of the method of makinga sanding pad for removing an organic coating from a substratecomprising the steps of: (a) blending a liquid polymeric material with anano-clay material to produce a first blend; (b) blending a cellulosicmaterial with said first blend to produce a second blend; and (c)extruding the second blend to form a continuous sheet of abrasivematerial into a plurality of individual pads.
 62. The product of themethod of claim 61 wherein after step (c) the continuous sheet ofabrasive material is cut into a plurality of pads.
 63. The product ofthe method of claim 62 wherein in step (a) an abrasive material is addedto the first blend.
 64. The product of the method of claim 63 whereinthe abrasive material is aluminum oxide.
 65. The product of the methodof claim 61 wherein in step (a) the nano-clay is montmorillonite. 66.The product of the method of claim 61 wherein in step (a) the polymericmaterial is a polyurethane.
 67. The product of the method of claim 61wherein the cellulosic material is alpha cellulose.
 68. The product ofthe method of claim 61 wherein in step (c) the second blend is foamextruded.
 69. The product of the method of claim 63 wherein the abrasivematerial is aluminum oxide grit.
 70. The product of the method of claim61 wherein in step (a) the polymeric material is heated.